Metal alloys are a mixture of metals and other materials, such as other trace amounts of metals. Pure aluminum is generally soft and highly ductile material. In particular, aluminum alloys can increase the mechanical strength and improve the scratch and dent resistance of a part. In general, pure aluminum can be anodized to form a relatively translucent and cosmetically appealing aluminum oxide coating. Some aluminum alloys can be anodized to form aluminum oxide coatings with satisfactory appearance—that is, having relatively translucent aluminum oxide coating. However, anodizing some aluminum alloys having a particular alloying element, or alloying elements in higher concentrations, can result in aluminum oxide coatings having a discolored appearance—such as a yellowed appearance. Thus, despite the mechanical advantages of using aluminum alloys compared to pure aluminum, some aluminum alloys cannot be anodized to form an aluminum oxide coating having a satisfactory appearance using conventional techniques.